Electrical machines, in particular starter devices of internal-combustion engines, which are subjected to dirt and moisture during rugged use in motor vehicles, are sealed and protected against corrosion in a known manner, by dip varnishing. In this case, it is disadvantageous that the varnishing generally takes place in a dipping process using varnishes which inherently and during processing require costly environmental protection measures because of the risk of explosion and to prevent hazardous emissions. It is furthermore disadvantageous that the motor housing, drive bearing and commutator bearing have a certain elasticity in the case of clamping bolts or tie rods which hold starter devices together. For example, it is necessary to counteract the vibration influences during operation of the motor vehicle. However, the varnishes become brittle after a certain period of time and are then always breaking out of the separating joints on the end sides of the motor housing. The inside of the motor is no longer sealed, dirt and moisture can penetrate, and lead to damage in the motor. In addition, corrosion damage occurs at the joint sections where there is no varnish.
The same also applies in general to electrical machines having the same or similar construction, with corresponding seals which are used, for example, in motor vehicles as generators, as small motors for other units such as windscreen wipers or, for example, also as drive motors in electric tools.
An electric motor for a starter device is already known, with a rubber tube pushed a motor housing a rubber tube, and covering in a waterproof manner only the separating joints at the end sides of the motor housing on which the drive and commutator bearings are arranged. In this case, it is disadvantageous that the rubber tube is a complicated and expensive moulded part. Furthermore, the rubber tube is provided on one end with a radially inwardly projecting holder and a hole through which a braided power supply cable is pushed. In addition, the rubber tube has annular inner shoulders distributed over its complete length, in order to serve as impact protection for the motor housing and the permanent magnets which are bonded to its inner wall.